A flexible drill bit comprising a proximal shank part for connection to a rotational-drive device, a distal part made up of a cutting tip that allows bone tissue to be drilled; and an intermediate shaft part extending between the proximal shank part and the distal part is known from the anterior patent US2013/0261628 of Jan. 7, 2013. The intermediate shaft part has, on the one hand, enough longitudinal suppleness to allow the drill bit to deform along a radius of curvature and, on the other hand, enough torsional strength to allow the drill bit to drill a hole in bone tissue.
A flexible shaft used for drilling a bore in bone tissue is also known, from the anterior U.S. Pat. No. 6,053,922 of Jul. 17, 1996. The flexible shaft is made up of a tubular element having an internal longitudinal bore over the entire length of said element and a suitably shaped flute which extends in a continuous spiral or in continuous segments around said tubular element. The tubular element comprises, at each opposite end of the shaft, on the one hand a cutting head and on the other hand a means of connection to a drive device.
It may be noted that the drilling devices of the prior art do not allow the intervertebral space situated between two vertebrae of a segment of spine to be drilled and milled by going through the pedicles of these vertebrae.
This is because the drilling devices of the prior art only drill into bone tissue in a substantially curved direction with no possible control over said radius of curvature and with no guarantee of the drilling point.